(Click on any
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The Compound -
Synair Por-a-Mold
2020. This is a soft two part Polyurethane rubber compound sold for making
molds. It's expensive ($50, + $15 for the release spray - Synlube 531) but has a lot of traction
- as used
by the
Hyland brothers. They did use PAM2020 not PAM111 as Dave states on his
site, the difference is that 2020 is transparent, 111 is off-white. I bought this from
Industrial Paint and Plastics. It has a shelf life of about a year
but it must be kept dry. It reacts with water so keep the bottles sealed.
It seems fairly benign but it's best not
to get it over your hands. It cleans up with alcohol.
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Update: Two days after using this
my hands developed a rash, which turned into small white blisters and dry
flakes. Now it might not be due to this stuff but I eventually was
able to get the MSDS from Synair. (I really think they should be obliged to
supply the MSDS sheets with the chemicals, but that's another issue)
Among other things Part B (the
yellow fluid) is classified as Hazard health category 3, Acute & Chronic.
"Warning! ... Inhalation of vapors may cause
respiratory tract irritation. Contact with skin and eyes may cause
irritation ... in susceptible individuals"
So I recommend wearing gloves and not
breathing the vapors.
Another warning is that it's highly
reactive with water, giving off CO2. This will not only cause the mix
to foam, but if water gets into the Part B bottle it could cause it to
burst.
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Measure the two parts exactly 1:1
- my first batch I did by eye and it never set properly. The second
batch I used a syringe. Mix thoroughly and pour into the mold. Oops
nearly forgot, spray the mold with release compound (or car wax polish)
first. |
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The mold is made of a short
section of ABS waste pipe. I just drilled a hole in a piece of
melamine for the wheel hub, centered the pipe round it and glued it down
with hot glue. Then I sprayed it with the release compound (a wax
spray). To get better adhesion to the wheel hubs I roughened them with
sandpaper and drilled lots of small holes in them to give the rubber
something to key to. |
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12 hours later you
can remove the mold. At the time of mixing the stuff is like warm
honey. 30 minutes later it's like cold honey. 12 hours later it's
cured enough that you can de-mold it but it takes 24-48 hours to cure
completely - providing you mixed it properly. |
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Don't leave them touching anything
while they cure, otherwise you'll get a flat spot. The funny looking
circles are the bits from the back of the hubs. |
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Super grippy! I haven't
measured the friction coefficient but it's as tacky as "The Man Show" |
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I also tried just dipping wheels
and hubs in one go. Update: Message to self. Wear gloves next time! |
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It kept dripping
for ages. When cured it didn't seem to have as much grip as the
molded tires, but still much better than the plain Tamiya tires |
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